Apparatus and method for producing pulp articles



Jan. 12,1965 J. E. FooTE 3,165,437

APPARATUS AND METHOD FOR FRODUCING PULP ARTICLES 'Filed May 2, 1,962 i JAMES E. Poom BY KAQL. LQFLOCS l ATTORNEY United States Patent-O 3,165,437 APPARATUS AND METHD FR PRDUCING PULP ARTICLES James E. Foote, Westport, Conn., assignor to Diamond National Corporation, New York, N.Y., a corporation of Delaware Filed May 2, 1962, Ser. No. 191,9 6 Claims. (Cl. 162-228) This invention relates to an improved pulp molding Y apparatus.

The use of molded pulp articles, such as meat trays, egg cartons, flower pots, etc. has become quite universal,

vgenerally because of the throw away character of the produced, must be rejected as imperfect due to excessive warpage, excessively thinned out sections, etc. The Warpage and lack of uniformity of the articles are generally due to lack of homogeneity of the article fiber occurring due to eddy currents in the pulp stock slurry tanks and washing away of the pulp preform on the suction molds after deposition, for example.

A primary object of the present invention is to provide novel apparatus anda novel method whereby the pulp yfiber of a pulp article is uniformly consistent and the bers are properly oriented in a substantially undisturbed condition whereby articles may be produced in controlled conditions without loss of time, excessive rejects, and without substantial modification of presently available equipment.

Another object of the present invention is to provide in tioned above, means whereby a pulp stock slurry is maintained in substantially constant movement within a slurry ftank to obviate occulation and channeling, and is presented to the effective surface of a suction die as a relatively homogeneous mass Without material ber disorientation or washing of the pulp preforms after they have been deposited on the suction molds.

Other objectsl and the nature and advantages of the instant invention will be apparent from the following va novel method and apparatus of the character menf description of an exemplary embodiment of the inven tion taken in Vconjunction with the accompanying drawings, wherein; Y

FIG. l is an essentially diagrammatic side elevation of the novel apparatus of the invention illustrating the manner in which molded pulp articles are produced thereby; and

FIG. 2 is an enlargedy fragmentary section taken substantially on the plane of line 2-2 of FIG. l.

Referring to the drawing in detail, the apparatus is indicated generally at 10 and comprises a pulp stock slurry tank indicated generally at 12, a circulating pump indicated generally at 14 and a molded pulp suction die carrier indicated generally at 16.

The pulp stock slurry tank 12 includes a stock reservoir 18 into which a suitable supply of pulp stock slurry is introduced; the reservoir 18 communicates with an inlet conduit 20 connected to a suitable circulating pump 22. The pump 22 communicates with an outlet conduit or line 24 connected to a stock inlet ow or manifold chamber 26. The chamber 26 includes a perforated upper wall 28 for introducing the pulp stock slurry into a substantially semi-cylindrical stock vat or tank 30. The level of the pulp stock slurry 32 is maintained above an out- 3,155,437 Patented Jan. l2, 1965 ICC let opening 34 communicating with the reservoir 18, and the stock .slurry will be constantly circulated through a lower primary chamber 36 of the vat 30 in the manner indicated by the direction arrows therein.

The rate of circulation of the pulp stock slurry Will be sucient to prevent channelingand occulation of the stock which is essential in order to produce pulp articles of a uniform quality.

Extending transversely of the primary chamber 36 and supported therein by means of angle brackets 38, for example, see FIG. 2, is a false bottom or baffle member 40 which includes a plurality of transverse apertures or perforations 42. It will be noted that the pulp stock slurry, as indicated by the direction arrows extending through the perforations 42 in FIGS. l and 2, will move above the false bottom 40 which essentially forms a sec- 'ondary chamber 44 above the primary chamber 36. The

rate of movement or velocity of the stock in the secondary chamber 44 is substantially less than the velocity in the chamber 36 and thus eddy currents and washing of a deposited pulp preform is maintained at a minimum. The transverse upper edges 46 and 4S of the false bottom member 40 extend essentially up to the level 32 at which the Vpulp slurry stock is maintained.

It will be noted in FIG. l that the bottom Wall of the vat 30 converges toward the false bottom member 49 to 'thus reduce the cross section of the primary chamber 36 from the entrance to the exit thereof. ln this manner the speed or Velocity of the slurry moving through chamber 36 will be substantially constant from the entrance to the exit, roughly compensating for the liquid and solids being withdrawn by the suction dies and preventing ilocculation from occurring.

Additionally, the thickness of the false bottom member 40 lwill be between the stock passing through chambers 36 and 44.

Any desired form of die or die carrier can be uilized, and in this exemplary embodiment there is disclosed the rotary type which includes a transverse support shaft Si) defining the axis of generation of the curvature of the upper surface 52 of the false bottom 4t). The shaft 50 extends through a suction manifold 54 communicating through a plurality of radially extending suction lines 56 to circumferentially spaced suction mold dies '58 mounted on the outer rim 60 of the carrier 16.

As is conventional in the art, a negative pressure vacuum will be intermittently communicated through suitable valve mechanisms (not shown) to the suction mold dies 58 when they are introduced into the secondary chamber 4t) of the pulp stock slurry vat. Accordingly,

v when suction is applied at the exposed effective surface of the suction mold dies 5S, a pulp preform will be ldeposited on the outer surface ofthe suction mold dies. The dies ondary chamber in which the stock slurry moves at a low velocity.

Extending transversely of each of the dies 58 and depending from the outer surface of the ring 66 are scraper or pusher bars 62 which are in essentially trailing relationship with respect to the direction of movement of the dies 58. The pusher bars or scraper plates 62 include a free lower edge 64 substantially in contact with the upper surface 52 of the false bottom 40 and the end portions thereof, and as indicated at 66, 68 in FIG. 2, terminate adjacent the inner surface of the sides '70 and 72, respectively, of the stock vat 30. The scraper plates or bars form forwardly thereof accumulator chambers 72 which are constantly or stepwise moving within the secondary chamber 44 and accumulate therein a relatively homogeneous well mixed slurry of relatively slowrrnoving pulp stock.

Thus, the perforations 42 in the false bottom 40, together with the pusher bars 62, give a quieting effect to the stock as it enters the molding area and minimizes the creation of eddy currents and washing of the deposited pulp preform.

Due Vto the fact that a relatively low velocity ow of the stock occurs inV the secondary chamber and in the accumulator chambers, the fiber of the stock, When de'- posited on the eilective surface of the suction dies 58, will be in optimum orientation for the purpose of producing a high quality, stable, and uniformly textured pulp article. After the article preform has been deposited on the outer effective surface of the suction mold dies 58 as it moves out of the secondary chamber 44, to subsequently be removed therefrom by means of suitable transfer apparatus approximately the same or close to the rate of movement of the forming dies, the false bottomprotects the preform from the higher kvelocity pulp stock moving through primary chamber 36. n

There is herein disclosed novel apparatus which presents a pulp stock slurry in an optimum condition for deposition on the effective surface of suction dies, and yet the pulp stock slurry is maintained at a substantially optimum velocity in ay primary chamber, WellV mixed therein, for the purpose of preventing channeling and iiocculation, and readily accessible to the secondary and accumulator chambers 44 and 72, respectively.

Additionally, there is disclosed a novel method Wherein the pulp slurry stock is introduced into a vat ata relatively high velocity, and communicated to moving accumulator chambers and a secondary chamber which dispose the slurry stock at the effective surfaces of suction mold dies with a minimum of washing of the pulp article preforms and with the liber of the pulp of the preforms being maintained in optimumy orientation in order to produce uniform articles having a minimum of warpage.

Although the invention shown is embodied in a preferred form, it is intended that the disclosure be illustrative rather than denitive. It will be obvious to those skilled in the art that various changes may be made Without departing from the spirit of the invention and there- 2..,In the apparatus as set forth inv claim 1 wherein said vat comprises a `perforated false bottom forming said primary and secondary chambers, the furthery improvement wherein saidscraper plate means extends transversely of the direction of movement of said molding die includes a lower free edge in substantial engagement ,with the upper surfaceof said false bottom for accumulating ahomogeneous pulp slurry in said accumulator chamber. f' f 3. Invthe apparatus of claim 1; the furtherrimprovement` wherein said `primary chamber has agraduated cross section from entrance to exit for compensating for material withdrawn by said molding die and'maintaining a substantiallyconstant rate of movement to material moving through said primary chamber.

4. In apparatus for forming molded pulp articles comprising a slurryvvat, means communicating kwith said vat to circulate a pulp stock therein to maintain the slurry in substantial agitation and homogeneity,V a primary cham-V ber'in said vat into which the pulp stock Vslurry is initially introduced, a secondary chamber in said vat and overlying and communicating With said primary chamber, a suction die carrier mounted above said vat and including at least one molding die thereon movable in one direction through said secondarychamber for receiving a pulp preform thereon, the improvement comprising acfore the invention is not to be limited to what is shown in the drawings and described in the specication, but only as indicated in the appended claims. f

What is claimed is: v 1. In apparatus for forming molded pulp articles comprising a slurry vat, means communicating with said vat to circulate a pulp stock thereinto maintain the slurry in substantial agitation and homogeneity, a primary chamber in said vat into which the pulp stock slurry is initially introduced, a secondary chamber in said vat and overlying and communicating with said primary chamber,

a suction die carrier mounted above said vat and includ-` ing at least one molding die thereon movable inV one v direction through said secondary chamber for receiving a pulp preform thereon,'the improvement comprising scraper plate means disposed in trailing relation to said one molding die and forming lforwardly thereof a mov-Y able pulp stock slurry accumulator chamber whereby a homogeneous pulp slurry will be deposited on said molding die.

cumulator chamber-forming means disposed in trailing relationship to said one molding die and forming forwardly thereof a movable pulp stock slurry accumulator chamber whereby a homogeneous pulp slurry will be deposited on said molding die.

5. The method of forming molded pulp articles'with a uniform liber .texture comprising the steps of;

(a) constantly circulating a pulp stock slurry through a primary chamber ata rate to prevent channeling and occulation;

(b) directing the constantly circulating pulp stock slurry through a secondary chamber at a rate of ow which is substantially less than the rate of flow into said primary chamber, said rate of flow through said secondary chamber being such that said stock is quiescent; (c) isolating, moving andl simultaneously suction depositing a portion of the pulp stock slurry in said secondary chamber from a moving accumulator chamber as an article Vpreform .on a suction die.

6. The method of claim 5; including the step of circulating the pulp stock'slurry'ein said primary chamber at an increasing velocityY proportionalk to the rate at which the pulp stock Vvslurry is suction deposited from said secondary chamber.

References Cited vin the le of thispatent UNITED STATES PATENTS 

4. IN APPARATUS FOR FORMING MOLDED PULP ARTICLES COMPRISING A SLURRY VAT, MEANS COMMUNICATING WITH SAID VAT TO CIRCULATE A PULP STOCK THEREIN TO MAINTAIN THE SLURRY IN SUBSTANTIAL AGITATION AND HOMOGENEITY, A PRIMARY CHAMBER IN SAID VAT INTO WHICH THE PULP STOCK SLUURY IS INITIALLY INTRODUCED, A SECONDARY CHAMBER IN SAID VAT AND OVERLYING AND COMMUNICATING WITH SAID PRIMARY CHAMBER, A SUCTION DIE CARRIER MOUNTED ABOVE SAID VAT AND INCLUDING AT LEAST ONE MOLDING DIE THEREON MOVABLE IN ONE DIRECTION THROUGH SAID SECONDARY CHAMBER FOR RECEIVING A PULP PREFORM THEREON, THE IMPROVEMENT COMPRISING ACCUMULATOR CHAMBER-FORMING MEANS DISPOSED IN TRAILING RELATIONSHIP TO SAID ONE MOLDING DIE AND FORMING FOR-
 5. THE METHOD OF FORMING MOLDED PULP ARTICLES WITH A UNIFORM FIBER TEXTURE COMPRISING THE STEPS OF: (A) CONSTANTLY CIRCULATING A PULP STOCK SLURRY THROUGH A PRIMARY CHAMBER AT A RATE TO PREVENT CHANNELING AND FLOCCULATION; (B) DIRECTING THE CONSTANTLY CIRCULATING PULP STOCK SLURRY THROUGH A SECONDARY CHAMBER AT A RATE OF FLOW WHICH IS SUBSTANTIALLY LESS THAN THE RATE OF FLOW INTO SAID PRIMARY CHAMBER, SAID RATE OF FLOW THROUGH SAID SECONDARY CHAMBER BEING SUCH THAT SAID STOCK IS QUIESCENT; (C) ISOLATING, MOVING AND SIMULTANEOUSLY SUCTION DEPOSITING A PORTION OF THE PULP STOCK SLURRY IN SAID SECONDARY CHAMBER FROM A MOVING ACCUMULATOR CHAMBER AS AN ARTICLE PREFORM ON A SUCTION DIE. 